The present invention relates to methods and systems for minimizing alien crosstalk between connectors. Specifically, the methods and systems relate to isolation and compensation techniques for minimizing alien crosstalk between connectors for use with high-speed data cabling.
In the field of data communications, communications networks typically utilize techniques designed to maintain or improve the integrity of signals being transmitted via the network (“transmission signals”). To protect signal integrity, the communications networks should, at a minimum, satisfy compliance standards that are established by standards committees, such as the Institute of Electrical and Electronics Engineers (IEEE). The compliance standards help network designers provide communications networks that achieve at least minimum levels of signal integrity as well as some standard of interoperability.
One obstacle to maintaining adequate levels of signal integrity, known as crosstalk, adversely affects signal integrity by causing capacitive and inductive coupling between the transmission signals. Specifically, electromagnetic interference produced by one transmission signal may couple to another transmission signal and thereby disrupt or interfere with the affected transmission signal. The electromagnetic interference tends to emanate outwardly from a source transmission signal and undesirably affect any sufficiently proximate transmission signal. As a result, crosstalk tends to compromise signal integrity.
The effects of crosstalk increase when transmission signals are more proximate to one another. Consequently, typical communications networks include areas that are especially susceptible to crosstalk because of the proximity of the transmission signals. In particular, the communications networks include connectors that bring transmission signals into close proximity to one another. For example, the conductive pins of a traditional connector, such as a jack, are placed proximate to one another to form a convenient connection configuration, usually within the compact spaces of the connector. While such compact pin arrangements may be physically economical as a convenient connecting medium, the same pin arrangements tend to produce nightmarish crosstalk between the pins.
Due to the susceptibility of traditional connectors to crosstalk, conventional communications networks have employed a number of techniques to protect the transmission signals against crosstalk within the connector. For example, different arrangements or orientations of the connector pins have been used to reduce pin-to-pin crosstalk. Another known technique includes connecting the pins to conductive elements that are relationally shaped or positioned to induce coupling that tends to compensate for the crosstalk between the pins. Another compensation technique involves connecting the pins of a connector to conductive elements of a printed circuit board (PCB), with the conductive elements being relationally positioned or shaped to cause compensational coupling between them.
Intra-connector techniques for combating crosstalk, such as those described above, have helped to satisfactorily maintain the signal integrity of traditional transmission signals. However, with the widespread and growing use of computers in communications applications, the ensuing volumes of data traffic have accentuated the need for communications networks to transmit the data at higher speeds. When the data is transmitted at higher speeds, signal integrity is more easily compromised due to increased levels of interference between the high-speed transmission signals carrying the data. In particular, the effects of crosstalk are magnified because the high-speed signals produce stronger electromagnetic interference levels as well as increased coupling distances.
The magnified crosstalk associated with high-speed signals can significantly disrupt the transmission signals of conventional network connectors. Of special concern is one form of crosstalk that traditional connectors were able to overlook or ignore when transmitting traditional data signals. This form of crosstalk, known as alien crosstalk, describes the coupling effects between connectors. For example, high-speed data signals traveling via a first connector produce electromagnetic interference that couples to high-speed data signals traveling via an adjacent connector, adversely affecting the high-speed data signals of the adjacent jack. The magnified alien crosstalk produced by the high-speed signals can easily compromise the integrity of the transmission signals of an adjacent connector. Consequently, the transmission signals may become unrecognizable to a receiving device, and may even be compromised to the point that the transmission signals no longer comply with the established compliance standards.
Conventional connectors are ill-equipped to protect high-speed signals from alien crosstalk. Conventional connectors have largely been able to ignore alien crosstalk when transmitting traditional data signals. Instead, conventional connectors utilize techniques designed to control intra-connector crosstalk. However, these techniques do not provide adequate levels of isolation or compensation to protect from connector-to-connector alien crosstalk at high transmission speeds. Moreover, such techniques cannot be applied to alien crosstalk, which can be much more complicated to compensate for than is intra-connector crosstalk. In particular, alien crosstalk comes from a number of unpredictable sources, especially in the context of high-speed signals that typically use more transmission signals to carry the signal's increased bandwidth requirements. For example, traditional transmission signals such as 10 megabits per second and 100 megabits per second Ethernet signals typically use only two pin pairs for propagation through conventional connectors. However, higher speed signals require increased bandwidth. Accordingly, high-speed signals, such as 1 gigabit per second and 10 gigabits per second Ethernet signals, are usually transmitted in full-duplex mode (two-way transmission over a pin pair) over more than two pin pairs, thereby increasing the number of sources of crosstalk. Consequently, the known intra-connector techniques of conventional connectors cannot predict or overcome alien crosstalk produced by high-speed signals.
Although other types of connectors have achieved levels of isolation that may combat the alien crosstalk produced by high-speed transmission signals, these types of connectors have shortcomings that make their use undesirable in many communications systems, such as LAN communities. For example, shielded connectors exist that may achieve adequate levels of isolation to protect high-speed signal integrity, but these types of shielded connectors typically use a ground connection or can be used only with shielded cabling, which costs considerably more than unshielded cabling. Unshielded systems typically enjoy significant cost savings, which savings increase the desirability of unshielded systems as a transmitting medium. Moreover, conventional unshielded twisted pair cables are already well-established in a substantial number of existing communications systems. Further, inasmuch as ground connections may become faulty, shielded network systems run the risk of the ungrounded shields acting as antennae for electromagnetic interference.
In short, alien crosstalk is a significant factor for protecting the signal integrity of high-speed signals being transmitted via data communications networks. Conventional network connectors cannot effectively and accurately transmit high-speed data signals. Specifically, the conventional connectors for use in unshielded cabling networks do not provide adequate levels of compensation or isolation from alien crosstalk.